Glazing structures which have the ability of excluding at least part of the solar energy incident thereupon have been recognized as being eminently desirable especially in architectural applications. For instance, large buildings especially those of multi-story construction often utilize large expanses of glazing material in the outer walls thereof for aesthetical as well as functional reasons. A major drawback associated with such building structures is that they are characterized by a high heat load due to the solar radiation incident upon the large expanses of the glazing material thereof: this is the so-called "greenhouse" or "hothouse" effect. Attempts to reduce the undesirable effects of solar radiation have included adding tinting or pigmenting agents to usually monolithic glazing material. The tinting technique utilizes an absorption mechanism to reduce the transmission of solar energy and, for this reason, it is of only limited success. Attempts to reduce solar energy transmission to a high degree by absorption results only in increasing the temperature of the glazing material so that much of the absorbed energy is still transmitted by or through the glazing material by convective and reradiative processes. Further efforts to avoid the greenhouse effect and circumvent the shortcomings of the tinting technique have included depositing a layer or film of reflective material on the exposed outer surface of the glazing material. Such layers have also been deposited on glazing material by vacuum metalizing techniques whereby a partially optically transparent film of metal is deposited directly on the one surface of a glazing structure which is destined to become the interior surface of a glazing unit. The principal disadvantage of this system is that the uniform deposition of partially reflective films over large areas is technically difficult and, as a result, glazing structures of this type are expensive and the use thereof has been limited. Accordingly, the principal object of the present invention is to provide an optically transparent film structure of polyvinyl acetal having a high degree of solar radiation reflectivity.